1. Field of the Invention
The present invention relates to a lighting apparatus for vehicles such as motor vehicles, and more specifically, to a vehicle lighting apparatus comprising lamp deflection angle controlling means for controlling the changes in direction of beam of the lamp corresponding to the traveling conditions, for example, an adaptive front-lighting system (hereinafter referred to as AFS) More specifically, the present invention relates to a vehicle lighting apparatus being capable of smooth control of the changes in direction of radiation.
2. Description of the Related Art
The AFS proposed for enhancing driving safety of motor vehicles detects information on the steering angle of the steering wheel SW of the motor vehicles, the vehicle speed, and other traveling conditions of the motor vehicles by the sensor 1, and the detected output is input to the electronic control unit 2 (hereinafter referred to as ECU) as shown in FIG. 1. The ECU 2 controls the swivel type lights 3R, 3L provided respectively on the left and right of the front portion of the motor vehicle, that is, the headlamps 3 that the direction of radiation can be deflected in the lateral direction based on the supplied sensor outputs. Such swivel type lights 3R, 3L may include, as a structure that can turn the reflector provided in the headlamp in the horizontal direction, a structure that can turn the reflector by the driving source such as a motor or the like. A mechanism for this turning is referred to as an actuator in this specification. According to the AFS in this type, by detecting the steering angle of the steering wheel or the lighting condition of the turn signal lamps while the vehicle is traveling on the curved road, and controlling the deflection of the direction of radiation of the swivel type light, the portion of the road ahead of the curve can be illuminated corresponding to the traveling speed of the motor vehicle, thereby being effective in improvement of driving safety.
In this AFS, the actuator is controlled to receive a signal from the steering sensor of the steering wheel and move the swivel type light by a required deflection angle based on the signal. Normally, step signals representing segments of angles obtained by dividing steering angle of the steering wheel are fed as the sensor outputs from the steering angle sensor of the steering wheel as shown in the upper graph in FIG. 12, and the deflection angle of the swivel type light is controlled to be changed step by step along with steering of the steering wheel as shown in the lower graph in the same figure. Therefore, the luminous intensity distribution characteristic of the swivel type lamp changes step by step, and thus the driver may have a sense of discomfort, and problems in traffic safety may arise. In order to solve these problems, the resolutions of the steering angle sensor and the actuator must simply be increased to reduce the widths of steps, and thus efforts has been made to improve the resolution of the actuator in various ways. However, since the resolution of the steering angle sensor is actually lower than the resolution of the actuator, the resolution of the entire AFS is tuned to the resolution of the steering angle sensor, and thus improvement of the resolution of the steering angle sensor is desired. However, it appears to be a reality that it is difficult to manufacture it in compact at a low cost. In this connection, in the actuator, the deflection angle of the swivel lamp 30 can be controlled step by step by 0.02xc2x0-0.03xc2x0, but in the steering angle sensor, the step signal is supplied approximately by 1xc2x0 of the steering wheel. Therefore, based on the step-oriented sensor outputs of the steering angle sensor, the actuator must control to the luminous intensity distribution characteristic of the swivel lamp by controlling the deflection angle step by step approximately by 0.3xc2x0.
As is described above, in the conventional AFS, it is difficult to avoid the step-by-step control of the luminous intensity distribution characteristic of the swivel type lamp. In this case, when the steering wheel is turned to a large extend and thus the amount of change in outputs from the steering angle sensor is large, the swivel type light follows this change and is deflected at a high speed, so that the deflection angle is controlled smoothly in appearance even when it is controlled step by step, thereby realizing relatively smooth control of the luminous intensity distribution characteristic of the swivel type light. However, when the steering wheel is turned to a small extent and thus the amount of change in sensor outputs from the steering angle sensor is small, the deflecting angle of the swivel type light is controlled at a low speed step by step. Therefore, it is apparent that the deflection angle of the swivel type light is controlled step by step in appearance, and thus the luminous intensity distribution characteristic of the swivel type light is not smooth, which makes the aforementioned problem that the driver may have a feeling of discomfort distinctive.
The object of the present invention is to provide a vehicle lighting apparatus in which a smooth control of the change in luminous intensity distribution characteristic of the swivel type light is realized even when the existing steering angle sensor for supplying the sensor outputs with large step widths is used.
According to the present invention, there is provided a vehicle lighting apparatus comprising lamp deflection angle controlling means including a steering angle sensor for detecting the steering direction of the vehicle and supplying the signal varying step by step and controlling the changes in deflecting angle of the lamp based on the outputs from the steering angle sensor, characterized in that the lamp deflection angle controlling means comprises arithmetic circuit means for calculating the time series moving average of the outputs from the steering angle sensor, and controls the changes in deflection angle of the lamp based on the outputs of the arithmetic circuit means. The arithmetic circuit means is preferably adapted to decrease the amount of data on the sensor outputs to be used for calculating the time series moving average when the amount of change in sensor outputs from the steering angle sensor is large in comparison with the case in which the amount of change is small. The arithmetic circuit means is preferably adapted not to calculate the time series moving average when the amount of change in the steering angle sensor is at a certain level or higher.
According to the present invention, the outputs having smaller step widths in comparison with the step widths of the sensor outputs from the steering angle sensor can be obtained by averaging the sensor outputs from the steering angle sensor on the time axis in the arithmetic circuit means, and the changes in deflecting angle of the lamp can be controlled by minute step widths by controlling the changes in deflection angle of the lamp based on these outputs. Even when the existing steering angle sensor supplying the sensor outputs with large step widths is used, the deflection angle of the lamp can be controlled by minute step widths, and thus smooth control of luminous intensity distribution characteristic of the swivel type light can be realized.